.DELTA..sup.8 -Tetrahydrocannabinol, the pyschoactive marijuana derived cannabinoid, binds to the CB1 receptor in the brain and to the CB2 receptor in the spleen. Activation of the CB2 receptor has been shown to result in suppression of the immune system (Mechoulam, Cannabinoids as Therapeutic Agents, CRC Press, Boca Raton, Fla. (1986)). Thus, drugs which selectively activate the CB2 receptor have great potential as immunomodulatory agents for preventing tissue rejection in organ transplant patients and as immunosuppressive agents for treating autoimmune associated diseases, (e.g., lupus erythematosus, rheumatoid arthritis, psoriasis, multiple sclerosis and inflammatory bowel diseases such as ulcerative colitis and Crohn's disease). CB2 receptor agonists also can be used as anti-inflammatory agents and as agents for suppressing peripheral and idiopathic pain.
Unfortunately, most known CB2 receptor agonists, including most cannabinoids, are non-selective in that they also stimulate the CB1 receptor. Activation of the CB1 receptor causes the sedative and pyschotropic effects which are associated with marijuanna use. As a consequence, there are few if any agents which can target the CB2 receptor without at the same time causing these undesirable side-effects. The full potential of therapies which modulate the immune system by selectively stimulating the CB2 receptor is unlikely to be realized without the further development of agents which are selective agonists of the CB2 receptor.